The present invention relates to new phenylalanine derivatives and the use of the phenylalanine derivatives as medicines. The present invention also relates to the compounds usable as therapeutic agents or preventive agents for inflammatory diseases in which α4 integrin-depending adhesion process participates in the pathology. It was reported that α4 integrins participate in rheumatoid arthritis, inflammatory bowel diseases, systemic lupus erythematosus, multiple sclerosis, Sjögren's syndrome, asthma, psoriasis, allergy, diabetes, cardiovascular diseases, arterial sclerosis, restenosis, tumor proliferation, tumor metastasis and transplantation rejection. The compounds of the present invention having an antagonistic effect on the α4 integrins are usable as therapeutic agents or preventive agents for the above-described diseases.
In the inflammatory reactions, it is generally understood that when a microorganism invades a tissue or when the tissue is injured, leukocytes play an important role for the exclusion of the microorganism or for the repair of the injured tissue. It is also widely understood that in such cases, leukocytes usually circulating in the blood must pass through the vascular wall and be newly supplied to the injured tissue. It has been elucidated that the infiltration of the leukocytes from the blood vessel into the tissue is carried out by integrin molecules which are a group of heterodimeric proteins expressing on the leukocytes. The integrin molecules are classified into at least 8 subfamilies (β1 through β8 subfamilies) depending on the β chains thereof. Known typical subfamilies are β1 and β3 subfamilies involved in the adhesion of cell ingredients to the extracellular matrix such as collagen and fibronectin; β2 subfamily involved in cell-to-cell adhesion in the immune system; and β7 subfamily which mainly participates in the infiltration of leukocytes into mucosal tissues (Shimizu et al., Adv. Immunol. 72: 325-380, 1999). As for the above-described α4 integrins, two kinds of molecules thereof are known. They are VLA-4 (very late antigen-4) molecule belonging to the β1 subfamily and comprising α4β1 chain and LPAM-1 (lymphocyte Peyer's patch HEV adhesion molecule-1) molecule belonging to the β7 subfamily and comprising α4β7 chain. Usually most of leukocytes circulating in the blood have only a low adhesion affinity for the vascular-endothelium cells and they cannot move out of the blood vessel. However, lymphocytes mainly comprising T cells and B cells are capable of moving out of the blood vessel by a so-called lymphocyte homing phenomenon wherein they move from the blood into the lymphoid tissue through the blood vessel wall and then they return into the blood through the lymphatic vessel under the physiological conditions. It is known that LPAM-1 molecules participate in the lymphocyte homing into the lymphoid tissue of an intestinal tract such as Peyer's patch (Butcher et al., Adv. Immunol. 72: 209-253, 1999). On the other hand, when an inflammation occurs, the vascular-endothelium cells are activated by cytokine and chemokine released from the inflamed tissue, the expression of a group of cell surface antigens (adhesion molecules) participating in the adhesion of leukocytes to the vascular-endothelium cells is caused, and a lot of leukocytes infiltrate out of the blood vessel toward the inflamed tissue through the adhesion molecules.
As the cell surface antigens on the vascular-endothelium cells participating in the adhesion of the leukocytes, there have been known E-selectin (adhesion molecule mainly participating in the adhesion of neutrophils), ICAM-1 and VCAM-1 mainly participating in the adhesion of lymphocytes, and MAdCAM-1 mainly participating in the adhesion of lymphocytes in the lymphoid tissue of an intestinal tract such as Peyer's patch (Shimizu et al., Adv. Immunol. 72: 325-380, 1999). It was reported that in those adhesion molecules, VCAM-1 acts as a ligand of both VLA-4 and LPAM-1 and that MAdCAM-1 acts as the ligand of LPAM-1. As a ligand of both VLA-4 and LPAM-1, fibronectin which is a kind of extracellular matrix is also known (Shimizu et al., Adv. Immunol. 72: 325-380, 1999). The β1 integrin subfamily to which VLA-4 belongs comprises at least 6 integrins (VLA-1 to VLA-6) using extracellular matrixes such as fibronectin, collagen and laminin as the ligands. Many of integrins using extracellular matrixes as the ligands, such as VLA-5, β3 subfamily and β5 subfamily, recognize arginine-glycine-aspartic acid (RGD) sequence in fibronectin, vitronectin, tenascin and osteopontin. On the other hand, in the interaction of VLA-4 and fibronectin, the RGD sequence does not participate but a CS-1 peptide segment comprising leucine-aspartic acid-valine (LDV) as the core sequence participates (Pulido et al., J. Biol. Chem. 266: 10241-10245, 1991). Clements et al. found a sequence similar to LDV in amino acid sequences of VCAM-1 and MAdCAM-1. It has been elucidated that a variant obtained by partially modifying the CS-1-like sequence of VCAM-1 and MAdCAM-1 molecules cannot interact to VLA-4 or LPAM-1 (Clements et al., J. Cell Sci. 107: 2127-2135, 1994, Vonderheide et al., J. Cell. Biol. 125: 215-222, 1994, Renz et al., J. Cell. Biol. 125: 1395-1406, 1994, and Kilger et al., Int. Immunol. 9: 219-226, 1997). Thus, it was found that the CS-1-like sequence is important for the interaction of VLA-4/LPAM-1 and VCAM-1/MAdCAM-1.
It was also reported that the cyclic peptide having the CS-1-like structure is antagonistic both to the interaction of VLA-4 or LPAM-1 with VCAM-1, MAdCAM-1 or CS-1 peptide (Vanderslice et al., J. Immunol. 158: 1710-1718, 1997). The above-described facts indicate that all the interactions of α4 integrin and VCAM-1, MAdCAM-1 or fibronectin can be blocked by using a suitable α4 integrin antagonist (the term “α4 integrin antagonist” in the specification indicates a substance antagonistic to α4β1 and/or α4β7 integrin).
It is also known that the expression of VCAM-1 in vascular-endothelium cells is caused by inflammatory factors such as LPS, TNF-α or IL-1 and that when the inflammation occurs, the infiltration of the leukocytes from the blood vessel into the tissue is carried out by the VLA-4/VCAM-1 adhesion mechanism (Elices, Cell 60: 577-584, 1990, Osborn et al., Cell 59: 1203-1211, 1989 and Issekutz et al., J. Eex. Med. 183: 2175-2184, 1996). Because VLA-4 is expressed on the surfaces of activated lymphocytes, monocytes, eosinophils, mast cells and neutrophils, the adhesion mechanism of VLA-4/VCAM-1 plays an important role for the infiltration of those cells into the inflamed tissue. It was reported that VLA-4 is expressed on various sarcoma cells such as melanoma cells, and it was also elucidated that the adhesion mechanism of VLA-4/VCAM-1 participates in the metastasis of these tumors. By investigating the expression of VCAM-1 in various pathological tissues, it was made apparent that the adhesion mechanism of this VLA-4/VCAM-1 participates in various pathological stages. Namely, it was reported that in addition to the activated vascular-endothelium cells, the expression of VCAM-1 is increased in the inflamed tissues in the patients with autoimmune diseases such as rheumatoid synovial membrane (van Dinther-Janssen, J. Immunol. 147: 4207-4210, 1991 and Morales-Ducret et al., J. Immunol. 149: 1424-1431, 1992), lungs and respiratory tract epithelium in asthma (ten Hacken et al., Clin. Exp. Allergy 12: 1518-1525, 1998) and allergic diseases (Randolph et al., J. Clin. Invest. 104: 1021-1029, 1999), systemic lupus erythematosus (Takeuchi et al., J. Clin. Invest. 92: 3008-3016, 1993), Sjögren's syndrome (Edwards et al., Ann. Rheum. Dis. 52: 806-811, 1993), multiple sclerosis (Steffen et al., Am. J. Pathol. 145: 189-201, 1994) and psoriasis (Groves et al., J. Am. Acad. Dermatol. 29: 67-72, 1993); atherosclerotic plagues (O'Brien et al., J. Clin. Invest. 92: 945-951, 1993), intestinal tissues of the patients with inflammatory bowel diseases such as Crohn's disease and ulcerative colitis (Koizumi et al., Gastroenterol. 103: 840-847, 1992 and Nakamura et al., Lab. Invest. 69: 77-85, 1993), inflamed tissue of Langerhans island of patients with diabetes (Martin et al., J. Autoimmun. 9: 637-643, 1996) and implants during the rejection of transplantation of heart or kidney (Herskowitz et al. Am. J. Pathol. 145: 1082-1094, 1994 and Hill et al., Kidney Int. 47: 1383-1391, 1995). The adhesion mechanism of VLA-4/VCAM-1 participates in these various diseases.
There are many reports showing that in vivo administration of VLA-4 or VCAM-1 antibody was effective in improving the diseases of animal models with those inflammatory diseases. Concretely, Yednock et al. and Baron et al. reported that the in vivo administration of an antibody against α4 integrins was effective in controlling the incidence rate or in controlling encephalomyelitis in the experimental autoimmune encephalomyelitis models, i.e. multiple sclerosis models (Yednock et al., Nature 356: 63-66, 1992 and Baron et al., J. Exp. Med. 177: 57-68, 1993). Zeidler et al. reported that in vivo administration of an antibody against α4-integrin was effective in controlling the incidence rate of mouse collagen arthritis (rheumatoid models) (Zeidler et al., Autoimmunity 21: 245-252, 1995). The therapeutic effect of an antibody against α4-integrin in asthma models was reported by Abraham et al. and Sagara et al. (Abraham et al., J. Clin. Invest. 93: 776-787, 1994 and Sagara et al., Int. Arch. Allergy Immunol. 112: 287-294, 1997). The effect of an antibody against α4-integrin in inflammatory bowel disease models was reported by Podolsky et al. (Podolsky et al., J. Clin. Invest. 92: 372-380, 1993). The effect of an antibody against α4-integrin and that against VCAM antibody in insulin-dependent diabetes models were reported by Baron et al. (Baron et al., J. Clin. Invest. 93: 1700-1708, 1994). It was made apparent with baboon models that the restenosis of a blood vessel after an angioplasty carried out because of arteriosclerosis can be inhibited by the administration of α4 integrin antibody (Lumsden et al., J. Vasc. Surg. 26: 87-93, 1997). It was also reported that α4 integrin or VCAM antibody is effective in inhibiting the rejection of an implant or inhibiting metastasis of a cancer (Isobe et al., J. Immunol. 153: 5810-5818, 1994 and Okahara et al., Cancer Res. 54: 3233-3236, 1994).
As described above, unlike VCAM-1, MAdCAM-1 which is a ligand of LPAM-1 is constitutively expressed on high endothelial venules (HEV) in the intestinal mucosa, mesenteric lymphatic nodes, Peyer's patch and spleen and it participates in the homing of mucosal lymphocytes. It is also known that LPAM-1/MAdCAM-1 adhesion mechanism not only has physiological roles in the homing of the lymphocytes but also participates in some pathological processes. Briskin et al reported an increase in the expression of MAdCAM-1 in inflamed regions in intestinal tracts of patients with inflammatory bowel diseases such as Crohn's disease and ulcerative colitis (Briskin et al., Am. J. Pathol. 151: 97-110, 1997). Hanninen et al. reported that induction of the expression is observed in an inflamed tissue of Langerhans island of NOD mouse which is a model of an insulin-dependent diabetes (Hanninen et al., J. Immunol. 160: 6018-6025, 1998). The fact that LPAM-1/MAdCAM-1 adhesion mechanism participates in the progress of diseases is apparent from the fact that conditions of mouse models with inflammatory bowel disease (Picarella et al., J. Immunol. 158: 2099-2106, 1997) and the above-described NOD mouse models are improved by the in vivo administration of antibody to MAdCAM or antibody to β7 integrin (Hanninen et al., J. Immunol. 160: 6018-6025, 1998 and Yang et al., Diabetes 46: 1542-1547, 1997).
The above-described facts indicate the possibility in that employing the blocking of VLA-4/VCAM-1, LPAM-1/VCAM-1 or LPAM-1/MAdCAM-1 adhesion mechanism by a suitable antagonist is effective in treating the chronic inflammatory diseases described above. The use of the antibody against VLA-4 as the VLA-4 antagonist is described in WO 93/13798, WO 93/15764, WO 94/16094 and WO 95/19790. Peptide compounds as VLA-4 antagonists are described in WO 94/15958, WO 95/15973, WO 96/00581 and WO 96/06108. Amino acid derivatives usable as VLA-4 antagonists are described in WO 99/10312, WO 99/10313, WO 99/36393, WO 99/37618 and WO 99/43642. However, none of them is practically used for the therapeutic treatment at present because of the lack of oral bioavailability and immunogenic properties during the use of them for a long period of time.